First you will want to navigate to the Collections Settings.
You can do so by clicking into the Collection > gear icon
Or by going to Network Settings > Spaces and Collections > View All Collection and selecting the three dot menu next to the Collection name. A Collection name can be up to 40 characters long.
You can also click on the Collection in the left hand navigation and select the three dot menu > Settings
From there, select Collection Details
And choose a new name for your Collection!
To learn how to manage your Collection settings, check out “How Do I Manage My Collections?